i love you most
by bravevulnerability
Summary: "You're the only one I want touching me." Based off the promo for 6x18. One shot.


**A/N: Picks up from the end of ABC's promo.****  
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* * *

_You were making out with a geisha?_

Kate tiredly pinched her nose between her thumb and forefinger. "Maybe I should stay at my place tonight."

"Kate," he huffed, reaching for her hand, but she skirted his touch and continued on towards their bedroom, her lips pressed together tightly the entire time.

Did she even have clothes at her place? Half of his closet housed a large majority of her wardrobe, her coats hanging parallel to his, her shoes lining the low shelves. She would likely have to pack a bag just to stay at her own apartment.

Rick sighed, followed her and called her name before she could make it through the office. She reluctantly came to a halt.

"Don't go."

She glanced up at him from the bedroom's doorway, accusation and hurt flaring bright in her eyes.

"Kate, the story I told you about the ninjas and the case and how that woman ended up kissing me - it was all true. I promise, I'm not-"

"It's not a matter of believing you," she snapped, propelling off the door with her fists clenched at her sides, and he was momentarily but thoroughly distracted by how devastatingly _hot_ she was when she was seething with anger.

He had never seen her so jealous before.

She had always tried to hide any envy she had ever felt over him in the past, always forced it into nothing more than a subdued flicker in her eyes, but tonight it blazed like wildfire.

"I believe your story, Castle, but I don't want another woman touching you, _kissing_ you," she spit the words out like acid. "I should be the only one allowed to do that."

"You are," he insisted vehemently. "You're the only one I want touching me."

"Yeah? Well, that's kind of hard to believe when you keep ending up with other women on top of you," she retorted, a glint of resentment catching in her gaze, but still the hurt overcompensated. And he understood, he did. She trusted him, knew he would never cheat on her, but he could see she still burned with the mental image of another woman taking advantage of what his fiancé was blatantly claiming as hers.

His brief lip lock with the geisha hadn't been planned, nor welcome, and he knew from experience that if the roles were reversed, he'd be just as indignant as Kate currently was. He couldn't blame her, but he did hope to instill some reassurance.

"I should never have let it go that far," he said solemnly, still kicking himself for allowing this kind of situation to happen. Twice. He was on thin ice here. "I should have stopped it sooner."

Her arms were crossed tightly over her chest and her jaw was squared so firmly he was sure it could cut, but he saw her wavering, her lower lip trembling just barely with it. And he took his opportunity to fix this.

"Kate, you know you're the only one I will ever want," he said, moving closer to her stiff figure. He skimmed his hands down her arms, took it as a positive sign when she didn't brush him off. "No other woman could ever measure up to you, and I _know_ you know that."

She still refused to budge, so stubborn and skeptical even after two years together, and he hooked a careful arm around her waist even as she kept her eyes to the ground.

"Want me to prove it?"

Her eyes slid up to his, the hurt, the uncertainty, the vicious irritation - all washed away by the sudden spark of carnal heat.

"Yes."

* * *

Kate gasped when he lowered his mouth to the smooth plain of her neck, doing wicked things with his scalding tongue that made her knees weaken and her body sway into his. She felt him smirk against her skin and jerked his head away from her neck by the grip of her fingers in his hair, crushed her mouth to his - biting, nipping, punishing him in the best way she knew how.

He groaned, pinned her to the wall with the press of his hips but tore away from her lips.

"Do you trust me?" he asked suddenly, and her eyes fluttered open, drifted to see him staring back at her intently, cloudy with lust and a hint of hesitation. She didn't ever want him to hesitate.

Kate nodded, no longer trusting her voice – probably already gravelly with her crackling need for him. She _did_ trust him, she believed his tale about the geisha who took advantage of his natural kindness and the ninjas who invaded just as he was putting the woman away, but it still made her blood simmer to know someone else had had their hands on the man she was marrying. It made images of a bikini-clad reporter from over a year ago flood her mind and flashbacks from that occurrence were the last thing she needed tonight.

Castle's hand snaked into her hair, devastating the neat bun she had swept it into that morning, and she tilted her head to the side, let him trail his mouth down the side of her neck, pausing at the vivid thud of her pulse to scrape his teeth there.

"I like the way you taste," he husked into her ear, tugging her hips deeper into the cradle of his with one hand while the other worked on the buttons of her blouse. "The sounds you make," he added, cupping one of her breasts in his hand and squeezing lightly, teasing his thumb over the lace covering her nipple and forcing a low whine from her throat to accentuate his point. "How you bite your lip, even when we're alone, to hold them in."

She ground her teeth together to refrain from doing exactly what he had just said and fisted her hands in his shirt, used her stance against the bedroom's doorway to drive them forward, push him down into his office chair before he could even realize what she was planning. He grunted, tried to sit up, but she went for his belt, working his zipper down and slipping her hand inside his boxers as her knees hit the floor.

"Beckett," he choked out, reaching for her hair. His fingers were gentle as they carded through the locks, coming to rest at her nape, but there was nothing gentle about what they were doing tonight and she swatted his hand away. This was about staking claim.

She jerked his pants down, grinned when his hips rose to assist.

"I like the sounds you make too, Castle," she breathed hotly over his erection, stroking him firmly in her hand, circling her thumb over the tip and watching him squirm for her.

"Beckett - Kate - you can't-"

She closed her mouth around him, cupped his balls in her hand as she swallowed and he cursed. She felt more than heard the moan reverberate through his body while she hummed softly, worked her throat against him, and flicked her eyes up to see his hands white knuckled and clenched in a death grip around the arms of the chair, teeth grit fiercely to hold it all in. He wasn't the only one who took notes. She loved to watch him too, catalogue the assortment of expressions and noises he made as she tortured him in all of her favorite ways.

"Fuck," he hissed as she slowly – so purposefully slow – scraped her teeth up his cock, feeling her own body growing wet with anticipation. "How could you even think-"

He was trying so hard not to thrust his hips into her, but when she swirled her tongue, twisted her fingers around his base, she felt the growl ripple through his frame, and then he was hastily reaching for her, hauling her into his lap.

He pushed her jeans down roughly and she could hear him grumbling about how the denim was too tight and _we should already be naked here, Beckett_.

She concurred as she expertly unbuttoned his shirt, shoved it from his shoulders and pressed her open mouth to his shoulder, made a path with her tongue along his collarbone, his neck, his jaw.

All hers.

He ripped her underwear as he was tearing them off of her, and she nipped hard at his cheek for it because those were her favorite pair, but she didn't have the time to complain before he was abruptly gliding inside her.

* * *

She breathed a moan into his ear as he thrust inside without warning, pushing deep into the welcoming heat of her, and he hoped he was proving it, proving that he meant every word. He'd never had such an intense physical connection with anyone else, not even _close _to what he had with Kate. The way they fit together – in every sense – was unique, remarkable and uncanny. Something that could never be replicated with anyone else.

Her nails stabbed into his shoulders and her knees bruised when they clamped around him as he rose up, transferred her to the edge of the desk.

She was scorching and soaked around him as she took him deeper with every stroke, her lips sucking determinedly at his neck, causing another searing wave of heat to course through him. She was determined to mark him and it made his arousal grow to impossible heights, because he fucking _loved_ the possessive side of Kate Beckett.

Her legs tightened around him, her hips picking up speed in their rhythm against his, and within seconds his thrusts were faltering, growing sloppy and out of control. Both of her hands came to his face and he met the piercing, feral darkness in her gaze with his own.

"You're mine," she whispered, softer than he expected, less of a claim and more of a promise, and he pressed her impossibly closer with his hand at the base of her spine. She arched and he felt her walls tighten and narrow around him, so close and making him lose himself with it. He plunged into her harder, relentlessly until she cried out her release, her head falling back and her hands fisting brutally in his hair, dragging him with her.

* * *

Kate slumped forward, into the wall of his trembling body as she floated back down. His arms were strong around her even as the last waves of his orgasm shuddered through him, palms migrating up the curved path of her vertebrae to meet at her neck, smoothing away the hair stuck to her skin and coaxing her face upwards.

Space was currently nonexistent between them and all she had to do was lean forward to smudge her lips over his, leisurely trace her tongue along the seam of his mouth.

"How's the hickey looking?" he murmured when she dropped her forehead to his shoulder and she grunted a laugh, slid her eyes to the purposeful bite she had left on the side of his neck.

"Not bad," she grinned, fingers fluttering over the slow bloom of red at the bottom of his throat. She hadn't planned to intentionally mark him with her mouth, but once she had started, it had been too late to stop. "May want to pull out a scarf for tomorrow."

He huffed in amusement, released a sigh of contentment as he held her.

"You're it for me," he said suddenly, lips ghosting over her temple as he spoke. "You're everything, only you."

His words held a sense of finality and it made her still calming heart start up a new, erratic cadence against her ribs. She had already known this, that he was her one and done and that it was mutual for him, but to hear it put so bluntly, so clearly – she hadn't known she needed it.

"How could you ever think I'd want anything else but this?" he added in a whisper at the cove of her neck and she snaked her arms around his waist, hugged him to her tightly.

"Castle?"

"Hmm?"

"The lease on my place is almost up."

"Oh?" He lifted his head, smothering a smile because she was sure he already had an idea of where she was going with this, why she had brought it up.

She practically lived here as it was, the majority of her belongings and essentials already having their own residence in the loft. Keeping her apartment had been a nice safety net, a place to go when she needed peace or when they needed some time alone without the risk of interruption. But it had stopped feeling like home long ago.

"Move in with me, Kate. Completely."

She nodded, curled her fingers around his ear out of habit and matched his smile.

"Okay."

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**As usual, I greatly dislike it, but thank you to any who took the time to read. Feedback is always welcome and appreciated.**

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